In the production of cultured whey products such as described in my U.S. Pat. Nos. 3,343,962, Sept. 26, 1967 and 3,497,359, Feb. 24, 1970 a mother culture is produced by culturing Lactobacillus acidophilus in a milk nutrient base in the presence of cobalt carbonate. This conditions the organisms to become tolerant to a higher acidity condition than usually expected from Lactobacillus acidophilus, a desirable characteristic.
It has now been found however that at least some Lactobacillus acidophilus strains are sensitive to addition of metallic ions such as obtained in the presence of cobalt carbonate, a phenomenon that may be termed metal poisoning. This is evidenced by lower acidity, dwarfing and clumping of the organisms.
Usual strains of Lactobacillus acidophilus can be expected to have a percent of acidity, expressed as Lactic acid, below 1.5. The desired strains are characterized by acidity rise to the order of 2% or greater.
The organism physical characteristics of a typical laboratory strain of Lactobacillus acidophilus show a size of three to five microns with thin rod-like structure, some bent and L-shaped and with a more or less loosely held, almost transparent outer sheath that tends to collapse and wrinkle.